Liquid crystal displays are commonly used as display devices for compact electronic apparatuses, because they not only provide good quality images but are also very thin. Because liquid crystal molecules in a liquid crystal display do not emit any light themselves, the liquid crystal molecules have to be lit by a light source so as to clearly and sharply display text and images. Therefore, liquid crystal displays usually require a backlight module.
Referring to FIG. 12, a typical backlight module 88 includes a light guide plate 880, a light source 882, and a reflector 884, arranged in that order from right to left. The backlight module 88 further includes a plastic frame 886 for receiving the light guide plate 880, the light source 882, and the reflector 884. The reflector 884 has a planar inner surface 885 facing the light source 882. The light source 882 interposed between the light guide plate 880 and the reflector 884 includes a plurality of light emitting diode (LED) units 888. Each LED unit 888 includes a red LED 888a, a green LED 888b, and a blue LED 888c, and each LED 888a/888b/888c can emit light beams of the one respective particular kind of primary color.
In operation, a mixing process of light beams occurs since each LED 888a/888b/888c emits one respective kind of light beams. The mixing process generally occurs in a space ranging from where the light beams emit from the LEDs 888a, 888b, and 888c to where the light beams reach the light guide plate 880, thus obtaining white light beams. However, the mixing space for the light beams is limited to a certain size of the plastic frame 886, and the mixed light beams are therefore liable to appear a little yellow or blue, instead of being pure white. This may result in an uneven color balance of light output by the backlight module 88. In order to obtain pure white light beams, the size of the plastic frame 886 is required to be large, which correspondingly increases a size of the backlight module 88. This makes the backlight module 88 unsuitable for certain compact and small-scale applications.
What is needed, therefore, is a backlight module that can overcome the above-described deficiencies. What is also needed is a liquid crystal display employing such a backlight module.